/* Copyright  (c) 2002 Graz University of Technology. All rights reserved.
 *
 * Redistribution and use in  source and binary forms, with or without 
 * modification, are permitted  provided that the following conditions are met:
 *
 * 1. Redistributions of  source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in  binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 *  
 * 3. The end-user documentation included with the redistribution, if any, must
 *    include the following acknowledgment:
 * 
 *    "This product includes software developed by IAIK of Graz University of
 *     Technology."
 * 
 *    Alternately, this acknowledgment may appear in the software itself, if 
 *    and wherever such third-party acknowledgments normally appear.
 *  
 * 4. The names "Graz University of Technology" and "IAIK of Graz University of
 *    Technology" must not be used to endorse or promote products derived from 
 *    this software without prior written permission.
 *  
 * 5. Products derived from this software may not be called 
 *    "IAIK PKCS Wrapper", nor may "IAIK" appear in their name, without prior 
 *    written permission of Graz University of Technology.
 *  
 *  THIS SOFTWARE IS PROVIDED "AS IS" AND ANY EXPRESSED OR IMPLIED
 *  WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 *  WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 *  PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE LICENSOR BE
 *  LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY,
 *  OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 *  PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA,
 *  OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
 *  ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 *  OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 *  OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 *  POSSIBILITY  OF SUCH DAMAGE.
 */

package demo.pkcs.pkcs11; 

import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.math.BigInteger;
import java.security.GeneralSecurityException;
import java.security.Security;
import java.security.Signature;
import java.security.cert.CertificateFactory;
import java.security.cert.X509Certificate;

import javax.crypto.Cipher;

import iaik.security.provider.IAIK;
import iaik.utils.Util;



public class VerifySignature {

  protected X509Certificate certificate_;

  protected Signature verifyEngine_;

  public VerifySignature(X509Certificate certificate, String algorithm)
      throws GeneralSecurityException
  {
    certificate_ = certificate;
    // verifyEngine_ = Signature.getInstance(algorithm, "IAIK");
    verifyEngine_ = Signature.getInstance(algorithm);
    verifyEngine_.initVerify(certificate.getPublicKey());
  }

  public boolean verify(InputStream data, byte[] signature)
      throws IOException, GeneralSecurityException
  {
    byte[] buffer = new byte[1024];
    int bytesRead;

    while ((bytesRead = data.read(buffer, 0, buffer.length)) >= 0) {
      verifyEngine_.update(buffer, 0, bytesRead);
    }

    return verifyEngine_.verify(signature) ;
  }

  public static void main(String[] args) {
    if (args.length != 4) {
      printUsage();
      System.exit(1);
    }

    try {
      FileInputStream dataInput = new FileInputStream(args[0]);
      byte[] signature = Util.readStream(new FileInputStream(args[1]));
      FileInputStream certificateInput = new FileInputStream(args[2]);
      Security.addProvider(new IAIK());
      //CertificateFactory certificateFactory = CertificateFactory.getInstance("X.509", "IAIK");
      CertificateFactory certificateFactory = CertificateFactory.getInstance("X.509");
      X509Certificate certificate = (X509Certificate) certificateFactory.generateCertificate(certificateInput);

      VerifySignature verifier = new VerifySignature(certificate, args[3]);

      if (verifier.verify(dataInput, signature)) {
        System.out.println("Verified signature successfully.");
      } else {
        System.out.println("Signature is INVALID.");
        Cipher rsa = Cipher.getInstance("RSA/ECB/NoPadding");
        rsa.init(Cipher.DECRYPT_MODE, certificate.getPublicKey());
        byte[] signedBlock = rsa.doFinal(signature);
        System.out.println("Decrypted signature value is (hex):");
        System.out.println(new BigInteger(1, signedBlock).toString(16));
      }

    } catch (Throwable thr) {
      thr.printStackTrace();
    }
  }

  public static void printUsage() {
    System.out.println("Usage: VerifySignature <data file> <signature file> <X.509 certificate file> <algorithm>");
    System.out.println(" e.g.: VerifySignature data.dat signature.bin signerCertificate.der SHA1withRSA");
  }


}